Cutting element arrangement for single roller cone bit

ABSTRACT

A cutting element arrangement for a single roller cone bit includes both at least one substantially non-planar cutting element and at least one substantially planar cutting element. The substantially non-planar cutting element is disposed on an inner row of the single roller cone and the substantially planar cutting element is disposed on an outer row of the single roller cone. With such an arrangement, the substantially non-planar inner row cutting elements effectively penetrate formations while the substantially planar outer row cutting elements maintain bore hole gage.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority, pursuant to 35 U.S.C. § 119(e), of U.S. Provisional Patent Application No. 60/484,172 filed Jul. 1, 2003. That Application is incorporated by reference in its entirety.

BACKGROUND OF INVENTION

1. Field of the Invention

The invention relates generally to the field of roller cone (“rock”) bits used to drill wellbores through earth formations. More specifically, the invention is related to an arrangement of cutting elements (“inserts”) used in roller cone bits having a single roller cone.

2. Background Art

Roller cone bits are one type of drill bit used to drill wellbores through earth formations. Roller cone bits include a bit body adapted to be coupled to a drilling tool assembly or “drill string” which rotates the bit as it is pressed axially into the formations being drilled. The bit body includes one or more legs, each having thereon a bearing journal. The most commonly used types of roller cone drill bits include three such legs and bearing journals. The roller cone is rotatably mounted to the bearing journal. During drilling, the roller cones rotate about the respective journals while the bit is rotated.

The roller cones include a number of cutting elements (also referred to and known as “inserts” or “teeth”), which may be press fit cutting elements made from tungsten carbide and other materials, or may be milled steel teeth. The cutting elements engage the formation in a combination of crushing, gouging, and scraping or shearing action that removes small segments of the formation being drilled.

The cutting elements on a cone of a three-cone bit are generally classified as inner-row cutting elements and gage-row cutting elements. Inner row cutting elements engage the bore hole bottom, but not the well bore wall. Gage-row cutting elements engage the well bore wall and sometimes a small outer ring portion of the bore hole bottom. The direction of motion of cutting elements engaging the rock on a two or three-cone bit is generally in one direction or a very small limited range of direction, i.e., 10 degrees or less.

One particular type of roller cone drill bit includes only one leg, bearing journal, and roller cone rotatably attached thereto. The drilled hole and the longitudinal axis of this type of bit are generally concentric. This type of drill bit has generally been preferred for drilling applications when the diameter of the hole being drilled is small (e.g., less than about 4 to 6 inches [10 to 15 cm]) because the bearing structure can be larger relative to the diameter of the drilled hole when the bit only has one concentric roller cone. This is in contrast to the typical three-cone rock bit, in which each journal must be smaller relative to the drilled hole diameter.

Similar to roller cones of a two-cone or three-cone rock bit, cutting elements are disposed around a surface of a single roller cone bit for penetrating into a formation. One type of cutting element that has been disposed around the surface of a roller cone is a substantially planar cutting element. Flat crested cutting elements are examples of substantially planar cutting elements. FIG. 1 shows a flat crested cutting element 10. Properties of the flat crested cutting element 10 include a relatively large surface area 12 for engaging a formation and sharp corners 14 for shearing action. Although substantially planar cutting elements 10 are effective in maintaining a gage of a bore hole, they are not effective in penetrating into hard formations.

Another type of cutting element that has been disposed around the surface of a roller cone is a substantially non-planar cutting element (also referred to as “non-flat crested cutting elements”). Conical cutting elements and chisel cutting elements are examples of substantially non-planar cutting elements. FIG. 2 shows a substantially non-planar cutting element 20. Properties of the substantially non-planar cutting element 20 include a relatively more pointed surface area 22 for engaging a formation.

Such substantially non-planar cutting elements may be characterized, or otherwise defined, as having a particular tip radius to extension ratio. For example, FIG. 3 shows how a conical cutting element 23 may be characterized in terms of a ratio of its tip radius 24 to its tip extension 26. Similarly, FIGS. 4 a and 4 b, which show front and side views of a chisel insert 25, show how the chisel insert 25 may be characterized in terms of a ratio of its tip radius 27 to its tip extension 28. Those skilled in the art will understand that the tip radius to extension ratio of a particular cutting element allows for the characterization of the “aggressiveness” of the cutting element in a general manner.

Although substantially non-planar cutting elements 20 are effective in penetrating into hard formations, they wear quickly relative to substantially planar cutting elements 10 and are not effective in maintaining a gage of a bore hole.

Accordingly, in situations in which the maintenance of bore hole gage is important, roller cones having all substantially planar cutting elements are used, and in situations in which penetration into hard formations is important, roller cones having all substantially non-planar cutting elements (including combinations of conical cutting elements and chisel cutting elements) are used.

SUMMARY OF INVENTION

According to one aspect of one or more embodiments of the present invention, a roller cone drill bit comprises a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, where the single roller cone has a plurality of cutting elements disposed at positions selected such that a majority of cutting elements adapted to engage a bottom of a bore hole are substantially non-planar cutting elements and a majority of cutting elements adapted to engage a wall of the bore hole are substantially planar cutting elements.

According to one aspect of one or more embodiments of the present invention, a roller cone drill bit comprises a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, where the single roller cone has at least one inner row of cutting elements comprising at least one substantially non-planar cutting element and at least one outer row of cutting elements comprising at least one substantially planar cutting element.

According to one aspect of one or more embodiments of the present invention, a roller cone drill bit comprises a bit body adapted to be coupled to a drill string, a bearing journal depending from the bit body, and a single roller cone rotatably attached to the bearing journal, where the single roller cone has at least one substantially planar cutting element and at least one substantially non-planar cutting element.

Other aspects and advantages of the invention will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a substantially planar cutting element.

FIG. 2 shows a substantially non-planar cutting element.

FIG. 3 shows a conical cutting element.

FIG. 4 a shows a front view of a chisel cutting element.

FIG. 4 b shows a side view of a chisel cutting element.

FIG. 5 shows a generalized cut away view of a single roller cone bit.

FIG. 6 shows a single roller cone bit in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION

As discussed above, typical roller cones have either all substantially planar cutting elements or all substantially non-planar cutting elements depending on whether gage maintenance or formation penetration is more important. What is needed, however, especially with the use of a single roller cone bit, is a design that facilitates both gage maintenance and effective formation penetration.

A general structure for a single roller cone bit which can be made according to various embodiments of the present invention is shown in cut away view in FIG. 5. The bit includes a bit body 1 made of steel or other high strength material. The bit body 1 includes a coupling 4 at one end adapted to join the bit body 1 to a drill string (not shown) for rotating the bit during drilling. The bit body 1 may include gage protection pads 2 at circumferentially spaced apart positions about the bit body 1. The gage protection pads 2 may include gage protection inserts 3 in some embodiments. The gage protection pads 2, if used, extend to a drill diameter 13 of the bit.

The other end of the bit body 1 includes a bearing journal 1A to which a single, generally hemispherically shaped roller cone 6 is rotatably mounted. In some embodiments, the cone 6 may be locked onto the journal 1A by locking balls 1B disposed in corresponding grooves on the outer surface of the journal 1A and the interior surface of the cone 6. The means by which the cone 6 is rotatably locked onto the journal 1A is not meant to limit the scope of the present invention. The cone 6 is formed from steel or other high strength material and may be covered about its exterior surface with a hardfacing or similar material intended to reduce abrasive wear of the cone 6. In some embodiments, the cone 6 will include a seal 8 disposed to exclude fluid and debris from entering the space between the inside of the cone 6 and the journal 1A. Such seals are well known in the art.

The cone 6 includes a plurality of cutting elements thereon at selected positions, which in various embodiments of the invention are cutting elements 5, 7 generally fit into corresponding sockets (not shown separately) in the outer surface of the cone 6.

The journal 1A depends from the bit body 1 such that it defines an angle α between the rotational axis 9 of the journal 1A and the rotational axis 11 of the bit body 1. The size of this angle α will depend on factors such as the nature of the earth formations being drilled by the bit. Nonetheless, because the bit body 1 and the cone 6 rotate about different axes, the motion of the cutting elements 5, 7 during drilling can be roughly defined as falling within a wall contacting zone 10, in which the cutting elements 7 located therein at least intermittently contact the outer diameter (wall) of the wellbore, and a bottom contacting zone 12, in which the cutting elements 5 located therein are in substantially continuous contact with the earth formations, and generally do not contact the outer diameter (wall) of the wellbore during drilling. The cutting elements 7 in the wall contacting zone 10 therefore define the drill diameter 13 of the bit.

The cutting elements 5, 7 may be made from tungsten carbide, other metal carbide, or other hard materials known in the art for making drill bit cutting elements. The cutting elements 5, 7 may also be made from polycrystalline diamond, boron nitride, or other super hard material known in the art, or combinations of hard and super hard materials known in the art.

Various embodiments of the present invention have a cutting element arrangement that uses substantially planar cutting elements having a range of motion falling within a bore hole wall contacting zone and substantially non-planar cutting elements (e.g., conical and/or chisel cutting elements) having a range of motion falling within a bore hole bottom contacting zone.

FIG. 6 shows an exemplary single roller cone bit 40 in accordance with an embodiment of the present invention. As shown in FIG. 6, an angular position of a cutting element of a single roller cone bit 40 may be defined as follows. A first angle α 60 is defined as a journal angle from a horizontal plane 62. A second angle θ 64 is defined as the angle between an axis 66 of a single roller cone 54 and an axis of a cutting element. The sum of the first angle α 60 and the second angle θ 64 can then be used to describe the angular position of a particular cutting element. Those skilled in the art will appreciate that the foregoing cutting element angular position description is applicable to describing an arrangement of cutting elements in all three dimensions. In other words, an angular position of a cutting element defined as the sum of the journal angle 60 from a horizontal plane 62 and an angle between an axis 66 of the single roller cone 54 and an axis of a cutting element applies to a three dimensional layout of the single roller cone bit 40.

With respect to the definition of cutting element angular position discussed above, substantially non-planar cutting elements (e.g., conical and chisel cutting elements) 48 may be selected and disposed at an angle preferably anywhere substantially between 0 degrees and 120 degrees. Substantially planar cutting elements (e.g., flat crested cutting elements) 50 may be selected and disposed at an angle anywhere substantially between 120 degrees and 175 degrees. Note that FIG. 6 is not to scale with respect to the indications of the angle measurements.

Accordingly, a single roller cone bit 40 is provided that has a cutting element arrangement for penetrating into hard formations while maintaining a full gage of a bore hole. In this arrangement, the substantially non-planar cutting elements 48 are selected and positioned so as to support most of the weight of the single roller cone bit 40. The shape of the substantially non-planar cutting elements allows them to penetrate a hard formation effectively.

The substantially planar cutting elements 50 are selected and positioned so as to maintain a substantially full gage of the bore hole. The shape of the substantially planar cutting elements 50 provides greater carbide volume for increased wear resistance necessary to maintain bore hole gage. Moreover, the sharp corners of the substantially planar cutting elements 50 allow the substantially planar cutting elements 50 to cut with an efficient shearing action.

In one or more embodiments of the present invention, a region for disposition or placement of the substantially planar cutting elements 50 may be at an angle anywhere substantially between about 125 degrees and about 165 degrees.

In one or more embodiments of the present invention, a region for disposition or placement of the substantially planar cutting elements 50 may be at an angle anywhere substantially between about 135 degrees and about 155 degrees.

In one or more embodiments of the present invention, a region for disposition or placement of the substantially planar cutting elements 50 may be at an angle anywhere substantially between about 140 degrees and about 150 degrees.

In one or more embodiments of the present invention, a substantially non-planar cutting element may be positioned such that a longitudinal axis of the substantially non-planar cutting element 48 resides along the same path as the vertical axis 65 of the single roller cone bit 40.

In a preferred embodiment of the present invention, the tip radius to extension ratio of a substantially non-planar cutting element is substantially equal to 0.3. However, in one or more other embodiments of the present invention, the tip radius to extension ratio of a substantially non-planar cutting element may be anywhere substantially between 0.2 and 0.5.

In one or more embodiments of the present invention, any of the substantially non-planar cutting elements 48 and the substantially planar cutting elements 50 may be arranged to extend greater than or equal to {fraction (7/16)} inches from the outer hemispherical surface of the single roller cone 54.

In one or more embodiments of the present invention, any of the substantially non-planar cutting elements 48 and the substantially planar cutting elements 50 may be arranged to extend greater than or equal to 0.55 inches from the outer hemispherical surface of the single roller cone 54.

In one or more embodiments of the present invention, any of the substantially non-planar cutting elements 48 and the substantially planar cutting elements 50 may be arranged to extend greater than or equal to {fraction (1/2)} inches from the outer hemispherical surface of the single roller cone 54.

In one or more embodiments of the present invention, any of the substantially non-planar cutting elements 48 and the substantially planar cutting elements 50 may be arranged to extend less than or equal to 0.6 inches from the outer hemispherical surface of the single roller cone 54.

In one or more embodiments of the present invention, the substantially non-planar cutting elements 48 may have a structure in which an exterior material of the substantially non-planar cutting element 48 is softer than an embedded region within the substantially non-planar cutting element 48. For example, the substantially non-planar cutting element 48 may be embedded with a diamond insert. Such a structure in which a core harder than an exterior of a cutting element is embedded within the cutting element allows the substantially non-planar cutting element 48 to be “self-sharpening” in nature, thereby increasing bit life and penetration effectiveness.

The differing ranges of degrees with respect to the placement of the substantially non-planar cutting elements 48 and the substantially planar cutting elements 50 may be defined by the regions on the single roller cone 46 designed to be the bore hole contacting zone and the wall contacting zone, respectively. In other words, when the single roller cone 46 shown in FIG. 6 is in operation, a majority of the cutting elements engaging a bottom of a bore hole are substantially non-planar cutting elements and a majority of the cutting elements engaging a wall of the bore hole (i.e., maintaining a gage of the bore hole) are substantially planar cutting elements.

Moreover, the single roller cone 46 shown in FIG. 6 may be described as having inner rows of cutting elements and outer rows of cutting elements. An inner row of cutting elements may be defined as a row of cutting elements falling within a particular range of degrees. Like with an inner row of cutting elements, an outer row of cutting elements may also be defined as a row of cutting elements falling within a particular range of degrees.

In one or more other embodiments, an inner row of cutting elements may be defined as a row of cutting elements for penetrating into a formation, or cutting away from a bottom of a bore hole. In such embodiments, an outer row of cutting elements may be defined as a row of cutting elements for cutting away from a wall of the bore hole, or maintaining a gage of the bore hole.

Advantages of the present invention may include one or more of the following. In one or more embodiments, a single roller cone bit has a cutting element arrangement effective in penetrating into hard formations and maintaining full gage of a bore hole. The cutting element arrangement includes substantially non-planar cutting elements positioned on a region of the single roller cone intended to engage a bottom of a bore hole and substantially planar cutting elements positioned on a region of the single roller cone intended to engage a wall of the bore hole.

While the invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope of the invention as disclosed herein. Accordingly, the scope of the invention should be limited only by the attached claims. 

1. A roller cone drill bit, comprising: a bit body adapted to be coupled to a drill string; a bearing journal depending from the bit body; and a single roller cone rotatably attached to the bearing journal, the single roller cone having at least one substantially planar cutting element and at least one substantially non-planar cutting element.
 2. The roller cone drill bit of claim 1, wherein the at least one substantially non-planar cutting element is any one of a conical cutting element and a chisel cutting element.
 3. The roller cone drill bit of claim 1, wherein the at least one substantially planar cutting element is a flat crested cutting element.
 4. The roller cone drill bit of claim 1, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element is formed of tungsten carbide.
 5. The roller cone drill bit of claim 1, wherein the single roller cone is substantially hemispherical in shape.
 6. The roller cone drill bit of claim 1, wherein an angular position of any cutting element is defined as the sum of (1) a journal angle from a horizontal plane and (2) an angle between an axis of the single roller cone and an axis of the cutting element.
 7. The roller cone drill bit of claim 6, wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between 0 degrees and 120 degrees.
 8. The roller cone drill bit of claim 6, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees.
 9. The roller cone drill bit of claim 6, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 125 degrees and 165 degrees.
 10. The roller cone drill bit of claim 6, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 135 degrees and 155 degrees.
 11. The roller cone drill bit of claim 6, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 140 degrees and 150 degrees.
 12. The roller cone drill bit of claim 6, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees, and wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between 0 and 120 degrees.
 13. The roller cone drill bit of claim 1, wherein the at least one substantially non-planar cutting element has a tip radius to extension ratio substantially equal to 0.3.
 14. The roller cone drill bit of claim 1, wherein the at least one substantially planar cutting element has a tip radius to extension ratio substantially between 0.2 and 0.5.
 15. The roller cone drill bit of claim 1, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends less than or equal to 0.6 inches from a surface of the single roller cone.
 16. The roller cone drill bit of claim 1, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to {fraction (7/16)} inches from a surface of the single roller cone.
 17. The roller cone drill bit of claim 1, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to 0.5 inches from a surface of the single roller cone.
 18. The roller cone drill bit of claim 1, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to 0.55 inches from a surface of the single roller cone.
 19. The roller cone drill bit of claim 1, wherein the at least one substantially non-planar cutting element is formed having a core harder than an exterior such that the substantially non-planar cutting element is self-sharpening.
 20. A roller cone drill bit, comprising: a bit body adapted to be coupled to a drill string; a bearing journal depending from the bit body; and a single roller cone rotatably attached to the bearing journal, the single roller cone having a plurality of cutting elements disposed at positions selected such that a majority of cutting elements adapted to engage a bottom of a bore hole are substantially non-planar cutting elements and a majority of cutting elements adapted to engage a wall of the bore hole are substantially planar cutting elements.
 21. The roller cone drill bit of claim 20, wherein the at least one substantially non-planar cutting element is any one of a conical cutting element and a chisel cutting element.
 22. The roller cone drill bit of claim 20, wherein the at least one substantially non-planar cutting element is formed having a core harder than an exterior such that the substantially non-planar cutting element is self-sharpening.
 23. The roller cone drill bit of claim 20, wherein the at least one substantially planar cutting element is a flat crested cutting element.
 24. The roller cone drill bit of claim 20, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element is formed of tungsten carbide.
 25. The roller cone drill bit of claim 20, wherein the single roller cone is substantially hemispherical in shape.
 26. The roller cone drill bit of claim 20, wherein an angular position of any cutting element is defined as the sum of (1) a journal angle from a horizontal plane and (2) an angle between an axis of the single roller cone and an axis of the cutting element.
 27. The roller cone drill bit of claim 26, wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between 0 degrees and 120 degrees.
 28. The roller cone drill bit of claim 26, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees.
 29. The roller cone drill bit of claim 26, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 125 degrees and 165 degrees.
 30. The roller cone drill bit of claim 26, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 135 degrees and 155 degrees.
 31. The roller cone drill bit of claim 26, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 140 degrees and 150 degrees.
 32. The roller cone drill bit of claim 26, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees, and wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between 0 and 120 degrees.
 33. The roller cone drill bit of claim 20, wherein the at least one substantially non-planar cutting element has a tip radius to extension ratio substantially equal to 0.3.
 34. The roller cone drill bit of claim 20, wherein the at least one substantially planar cutting element has a tip radius to extension ratio substantially between 0.2 and 0.5.
 35. The roller cone drill bit of claim 20, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends less than or equal to 0.6 inches from a surface of the single roller cone.
 36. The roller cone drill bit of claim 20, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to {fraction (7/16)} inches from a surface of the single roller cone.
 37. The roller cone drill bit of claim 20, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to 0.5 inches from a surface of the single roller cone.
 38. The roller cone drill bit of claim 20, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to 0.55 inches from a surface of the single roller cone.
 39. A roller cone drill bit, comprising: a bit body adapted to be coupled to a drill string; a bearing journal depending from the bit body; and a single roller cone rotatably attached to the bearing journal, the single roller cone having at least one inner row of cutting elements comprising at least one substantially non-planar cutting element and at least one outer row of cutting elements comprising at least one substantially planar cutting element.
 40. The roller cone drill bit of claim 39, wherein the at least one substantially non-planar cutting element is any one of a conical cutting element and a chisel cutting element.
 41. The roller cone drill bit of claim 39, wherein the at least one substantially planar cutting element is a flat crested cutting element.
 42. The roller cone drill bit of claim 39, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element is formed of tungsten carbide.
 43. The roller cone drill bit of claim 39, wherein the single roller cone is substantially hemispherical in shape.
 44. The roller cone drill bit of claim 39, wherein an angular position of any cutting element is defined as the sum of (1) a journal angle from a horizontal plane and (2) an angle between an axis of the single roller cone and an axis of the cutting element.
 45. The roller cone drill bit of claim 44, wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between 0 degrees and 120 degrees.
 46. The roller cone drill bit of claim 44, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees.
 47. The roller cone drill bit of claim 44, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 125 degrees and 165 degrees.
 48. The roller cone drill bit of claim 44, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 135 degrees and 155 degrees.
 49. The roller cone drill bit of claim 44, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 140 degrees and 150 degrees.
 50. The roller cone drill bit of claim 44, wherein the at least one substantially planar cutting element is disposed at an angle substantially between 120 degrees and 175 degrees, and wherein the at least one substantially non-planar cutting element is disposed at an angle substantially between 0 and 120 degrees.
 51. The roller cone drill bit of claim 39, wherein the at least one substantially non-planar cutting element has a tip radius to extension ratio substantially equal to 0.3.
 52. The roller cone drill bit of claim 39, wherein the at least one substantially planar cutting element has a tip radius to extension ratio substantially between 0.2 and 0.5.
 53. The roller cone drill bit of claim 39, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends less than or equal to 0.6 inches from a surface of the single roller cone.
 54. The roller cone drill bit of claim 39, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to {fraction (7/16)} inches from a surface of the single roller cone.
 55. The roller cone drill bit of claim 39, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to 0.5 inches from a surface of the single roller cone.
 56. The roller cone drill bit of claim 39, wherein any one of the at least one substantially planar cutting element and the at least one substantially non-planar cutting element extends greater than or equal to 0.55 inches from a surface of the single roller cone.
 57. The roller cone drill bit of claim 39, wherein the at least one substantially non-planar cutting element is formed having a core harder than an exterior such that the substantially non-planar cutting element is self-sharpening. 